She removes the jaws in the comic - See the cover of Issue 19s cover art. No arms no jaw.
Well if you are infected, your body is able to control the current level of [infection] thats in your system. But someone who has been overcome by the [infection] will have increased levels of it as their body can't contain it, so it ends up flowing through them like blood and water does in their system, and when they bite someone they introduce more of the [infection] into that persons blood stream. This added [infection] is enough to overcome the living persons natural defences and in time it kills them and reanimates them as zombies...
Make any sense?
Not really. If it were rabies or something, maybe, but it doesn't really make sense. If the bite was a fatal neck/artery wound, maybe due to the vital point bitten and thus bleeding out. But look at someone with HIV/Aids, they don't suddenly 'get more Aids' when bitten by someone else who has it. Same thing would apply here. Whatever's in the survivor's blood, assuming the virus' initial exposure killed on contact, makes the virus seem to be recessive until death. It wouldn't make sense that a simple light scratch on the arm or what have you should suddenly turn into a zombie. Honestly, I just chalk the whole confusion up to being a plothole.
Also, at your latest post, the zombies are more a distraction for herself, they're apparently her coping mechanism for the post-apocalyptic world. IIRC it's said ones her boyfriend, and the other her ex-husband.